| As an inland basin in the northwest arid region of China, with scarce rainfall and strong evaporation, Junggar basin is the typical area of fragile ecological environment, and the plain located north of Tianshan mountain is the economic and social centre in Xinjiang. Since 21 Century, the ecological environmental construction in the western arid areas had made some achievements in the process of Western Development, but partial improvement and overall deterioration is the current ecological environment status and ecological environment problem is still grim. Along with the unceasing enhancement of climate change and human activities, especially unreasonable exploitation and utilization of water resources, the phenomenon of ecological environmental degradation has arisen, such as natural vegetation degradation, soil salinization, land desertification and lake wetland atrophy, etc.,which threaten the regional ecological security and the sustainable development of economy and society. Therefore, it has important theoretical value and practical significance for the purpose of coordinated development between water resources development and ecological environment to study on ecological environment evolution and driving mechanism and explore the relationship between the regional water cycle and ecological environment.By linking formation and transformation of water resources and supergene eco-environment in arid as a main thread, based on LUCC theory, RS and GIS technology, the interaction mechanism between water circulation and ecological system was further analyzed,the evolution and problems of supergene ecological environment in Junggar basin was researched systematically,the driving mechanism of ecological environment evolution was analyzed quantitatively, and the assessment system of supergene ecological environment based on groundwater was constructed. The main achievements are as follows:(1) Through study of relationship between groundwater circulation and surface ecological environment, groundwater of typical watershed plain area has the control effect on supergene ecological environment, and growth index of different types of vegetation were logarithmic correlation with groundwater depth, soil water content, soil salt content.The ground water level controlled vadose zone soil moisture and salt content.So based on gruand water state variables, multidimensional critical identification index system to supergene ecological environment security of was constructed.(2) Take mechanism of the ecological response of groundwater circulation as the main line, the study area is divided into mountain, artificial oasis, natural oasis and desert, and natural waters five ecosystem types based on the characteristic in arid and water resources form evolution. Landsat satellite remote sensing image and field investigation are used as the basis for remote sensing interpretation to obtain ecological environment data of four periods in the study area. The characteristics of framework,dynamic state and evolution of ecological environment in junggar basin are analyzed based on LUCC theory system: The background and the matrix of the ecological environment in junggar basin are desert and mountain,artificial oasis, natural oasis ecosystem and natural waters plaques with inlaid in them.The area of desert ecosystem, natural oasis ecosystem and natural waters ecosystem was reduced while the area of artificial oasis ecosystem increased in recent 40 years. The degree of land use, land use dynamic degree and land use transfer matrix are analysed,and shows: degree of land use and the area of cultivated land and construction land increased overall, suggested oasisization and urbanization speed up in junggar basin; Permanent ice and snow mountain grassland area of all showed a trend of decrease, that solid reservoir, basin water resources, water conservation function is on the decline in basin.(3) On the basis of AVHRR NDVI and MODIS NDVI data, the maximum synthesis and time series data reconstruction technology are used to obtain the vegetation index time series data of different scales in the study area. The vegetation change of zhungaer basin and tianshan mountain in different time and space scales has been studied using the mean, standard deviation and the linear trend method, its general characteristics as follows:(1)basin scale: the mean NDVI is 0.158, 43.8% the study area is smaller than 0.2, that means there is a low vegetation coverage and fragile ecological environment overall the study area. Vegetation index in 1981-2006 annual variation show a weak increase trend by amplitude is 0.0004 / a. Mean NDVI in growing season space variation degree and the linear trend analysis show a larger standard deviation for many years in tianshan mountain plains and gobi belt. Imply this area is a sensitive region of ecological environment.the vegetation index showed a trend of increased in plain and high tianshan mountain, especially the first mentioned of two, and pedmont gobi vegetation index was significantly less trend for many years(2)As the key section of tianshan mountain plains, ecological environment of junggar basin is stronger vulnerable.The mean NDVI in growing season between 2001 and 2010 interannual amplitude is 29.336 / a, and vegetation coverage increased overall; Extreme increase vegetation areas are mainly concentrated in farmland vegetation area; Mild and moderate vegetation to reduce area mainly concentrated in low and middle mountainous sparse vegetation region, such as the gobi; Vegetation was reduced mainly concentrated on the edge of the wetland and water area.(4) A intensive study on the driving force of vegetation cover change in northern slope of Tianshan Mountain was carried on by using spatial analysis and statistical analysis method based on the date of DEM, meteorological, groundwater level, land-use types, population and GDP. It came into a conclusion that the vegetation cover in northern slope of Tianshan Mountain exists obvious vertical differentiation features. In general, the geological conditions and water resources distribution dominated the basic pattern of Tianshan Mountain’s supergene ecological environment while the change of hydrodynamic conditions and climate, groundwater dynamics and human activity were the driving factors in the process of local variation in pattern of the ecological environment. At an altitude of more than 700 m, the natural factors such as slope, slope direction, precipitation and temperature had great effect on regional vegetation change, however, in the altitude of less than 700 m, the area of plain oasis was influenced by land-use types, groundwater level, population and economic which varied from water and land resources development and utilization through human activity.(5) An index system of supergene ecological environment evaluation in the northern slope of Tianshan Mountain was built in view of groundwater dynamic based on groundwater ecological function. By using the system, the evaluation and prediction on study area’s supergene ecological environment through analytic hierarchy process(AHP) method turned out that the ecological environment present a seriously deteriorated trend in current exploitation of groundwater in the study area. Two schemes were proposed on the basis of ecological environment constrains, regulation and control scheme with current hydraulic engineering(Scheme A) and regulation and control scheme with trans-basin diversion(Scheme B), respectively. Scheme B had an advantage over Scheme A to help maintain the ecological environment of natural river and the dynamic balance of groundwater system. |
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